The aim of this study was to evaluate the effect of Lactobacillus acidophilus (LAC), exogenous enzymes of ZAD® (exogenous enzyme preparation) or their combination on feed conversion, and dressing of rabbits fed different treatments of sugarcane bagasse (SCB). Five rations were allotted randomly to five groups of New-Zealand White (NZW) rabbits (n=10) with initial live body weight of (838±42.4) g and 5 weeks of age. Rabbits were fed on diets with different sources of fiber as follows, (i) a control diet composed of 100% berseem hay and 0% SCB, (ii) 50% berseem hay and 50% untreated SCB (USCB), (iii) 50% berseem hay and 50% SCB treated with L. acidophilus (LAC), (iv) 50% berseem hay and 50% SCB treated with ZAD® (ZAD), and (v) 50% berseem hay and 50% SCB treated with a combination of LAC+ZAD® (LZ). Treatments of SCB with L. acidophilus, ZAD® and LAC+ZAD® had the highest feed conversion ratio than both USCB and control. The dressing percentage of rabbits that fed the LAC and LZ diets was higher (P<0.05) compared with that in the other groups. Performance index (PI) for LAC group was improved (P<0.05) compared to that for the other groups; however, PI for USCB group was the lowest (P<0.05). It could be concluded that treating SCB with L. acidophilus, exogenous enzymes of ZAD® or their combination improved feed conversion and performance with more positive effects with L. acidophilus than the other treatments.

For many years, ruminant nutritionists and microbiologists have been interested in manipulating the microbial ecosystem of the rumen to improve production efficiency of different ruminant species. Removal and restriction of antibiotics subtherapeutic uses from ruminant diets has amplified interest in improving nutrient utilization and animal performance and search for more safe alternatives. Some bacterial and fungal microorganisms as a direct-fed microbial (DFM) can be the most suitable solutions. Microorganisms that are commonly used in DFM for ruminants may be classified mainly as lactic acid producing bacteria (LAB), lactic acid utilizing bacteria (LUB), or other microorganism’s species like Lactobacillus, Bifidobacterium, Enterococcus, Streptococcus, Bacillus, Propionibacterium, Megasphaera elsdenii and Prevotellabryantii, in addition to some fungal species of yeast such as Saccharomyces and Aspergillus. A definitive mode of action for bacterial or fungal DFM has not been established; although a variety of mechanisms have been suggested. Bacterial DFM potentially moderate rumen conditions, and improve weight gain and feed efficiency. Fungal DFM may reduce harmful oxygen from the rumen, prevent excess lactate production, increase feed digestibility, and alter rumen fermentation patterns. DFM may also compete with and inhibit the growth of pathogens, immune system modulation, and modulate microbial balance in the gastrointestinal tract. Improved dry matter intake, milk yield, fat corrected milk yield and milk fat content were obtained with DFM administration. However, the response to DFM is not constant; depending on dosages, feeding times and frequencies, and strains of DFM. Nonetheless, recent studies have supported the positive effects of DFM on ruminant performance.